1. Field of the Invention
This invention relates to gas generators of a compact size and light weight for supplying a gas to inflate an inflatable safety cushion apparatus that is attachable to passive belt type restraints used in various vehicles including aircraft.
2. Description of the Prior Art
Various forms of restraints have been proposed in the prior art for the protection of vehicle occupants. Specifically, there have been provided inflatable seat belt-shoulder harness systems, and inflatable air bag systems. Inflatable belt and harness systems and inflatable air bag systems are designed to provide a greater degree of protection than the conventional seat belt and shoulder harness systems are capable of for the vehicle occupants.
The inflatable restraint systems of the prior art are complex and expensive, and are characterized by their longer than desirable "reaction time", that is the length of time required for inflation and effective constraining action on the user upon a crash impact. Additionally, the prior art inflatable restraint systems depend on the surrounding structure for functional support and are best suited for installation at the time of manufacture of the vehicle. Among the reasons for this is that the inflatable belt systems require, in addition to the use of a special inflatable belt, the mounting in the vehicle, of a pressurized gas supply or inflator that is connected to the inflatable belt by an elongated tube or pipe. The inflatable air bag systems involve mounting in the steering wheel hub and/or in the dashboard of the vehicle of a folded and compacted air bag that is inflatable to a relatively large volume, and a pressurized gas supply or gas generator.
With prior art inflatable belt-type restraint systems, the time required to transport the inflation gas from a remote source results in an undesirable delay in the inflation of the inflatable belt. This extends the reaction time of the system beyond a value that is optimum for protection of the user in the most comfortable manner. The relatively larger volume of the air bag, and the relatively large distance between the folded and compacted bag and the user that must be traversed by the inflated bag, upon a crash impact, to constrain the user also cause the reaction time of the inflatable air bag restraint systems to be longer than desirable. As a consequence, for both the inflatable belt and the inflatable air bag restraint systems of the prior art as proposed for use in automotive vehicles, the longer than desirable reaction time upon a crash impact tends to allow some movement of the user to occur, thus exposing the user to an undesirable shock of sudden, hard constraint.
There thus exists a need in the art for not only an improved restraint for the protection of the occupants of vehicles involved in crashes, but a need for an improved gas generator for supplying the gas to such a device in a rapid and direct manner.
There further exists a need for a compact, lightweight and effective gas generator to be used inside a safety cushion of the type described in commonly owned, co-pending patent application Ser. No. 152,922 filed on even date with the present application by Bliss W. Law, et al, now U.S. Pat. No. 4,348,037. Some gas generators which are located in their entirety within the inflatable bladder of an inflatable body and head restraint are shown in U.S. Pat. No. 3,905,615 to Schulman issued Sept. 16, 1975 and in U.S. Pat. No. 3,948,541 to Schulman issued Apr. 6, 1976. These do not however, solve the problem of compactness, lightness of weight and of a shape to provide maximum comfort and safety to the user.
Gas generators in the art have generally been cylindrical with the propellant about some central core in either a doughnut shape, concentric cylinders or discs. Such an arrangement tends to make them too bulky and too thick for use with safety cushions applied to safety harnesses.
The gas generator or inflator of the present invention inflates the safety cushion with an innocuous gas such as nitrogen and is entirely enclosed in the safety cushion. The inflator is attached to suitable sensor apparatus that detects and responds to crash impacts of the vehicle in which it is installed. In order to achieve a desirable compactness, and in particular, a flat, slim configuration suitable for attachment to the safety harness between it and the occupant, the inflator has dual side by side combustion chambers having longitudinal axes that lie in a common plane. The combustion chambers are filled with gas generant material that is ignitable by a central igniter located between them and also in side by side relationship with them thus providing a very flat, compact and safely shaped package for the gas generator which is at the same time capable of efficient and quick gas generation in sufficient quantity but in minimum size. The inflator contains appropriate filters and cooling means, and is capable of inflating the safety cushion within about 15 milliseconds. Such rapid inflation of the safety cushion apparatus contributes importantly to the attainment of a desirably short reaction time.